1. Field of the Invention.
Corner reflectors comprised of a plurality of radar reflecting surfaces may be used to practice radar procedures on at sea by ships and aircraft or as decoys to confuse an enemy radar system. Other uses might comprise identifying the position of a person or an object which is in distress or lost on land or at sea.
Corner reflectors are useful in that they are the most efficient way of retro-directing light or radar energy back to its source. The corner reflector ordinarily comprises three plane reflective surfaces set mutually perpendicular to each other so as to define the internal corner angle of a cube.
Such a reflector has the property of reflecting along a path parallel to the incident pathways striking any of its surfaces from any direction within the solid angle defined by the surfaces.
2. Description of the Prior Art.
Corner reflectors have been constructed by connecting together a number of plane surfaces made of rigid material such as sheet metal; by connecting together a number of panels made of a flexible, collapsible lightweight material having a reflecting material adhered thereto; or by connecting together a number of panels made of a flexible, collapsible metallic fabric. The later two types of reflectors require the use of a rigid frame work or other support structure for maintaining the reflector in a proper reflecting condition. In addition, if the reflector is to be used on water, some means must be provided for maintaining the reflector above the surface of the water.
Inflatable structures have been effectively used to suspend and support a radar reflector in various types of environments. One commonly used type of inflatable structure is an inflatable spherical balloon having some means for suspending the reflector inside of the balloon. Such a balloon, when inflated with gas, exerts a uniform radial tension, which is an important factor in reducing the number of surface imperfections. However, the spherical balloon is not entirely satisfactory. One disadvantage of using a balloon as a support structure is that it is difficult to construct, therefore resulting in relatively high construction cost. Another disadvantage of a spherical balloon is that a relatively large volume of gas is required to inflate it; therefore, this type of unit is best suited for small sizes.
U.S. Pat. Nos. 3,217,325 and 3,276,017 are examples of inflatable support structures wherein a foam such as polystyrene foam may be used to either rigidize the support or the panels forming the corner reflector. In U.S. Pat. No. 3,217,325, the support structure is inflated with a hardenable foam substance so that a rigid support structure is formed after the foam hardens. In U.S. Pat. No. 3,276,017, the corner reflector is formed of fabric comprising two sheets with a gap therebetween which is then filled with a foam hardenable substance.